I just had my new engine broken in and dynoed. Its a 383 stroked to 434. Its got edelbrock heads, a comp cams xe275hl cam, 9.7:1 compression. I use 91 octane gas. the carb is a 750 DP with 71/78 jets. The timing is set at 12/30 if i remember correctly. i have the idle at 850. On the dyno it made 375hp/401tq at the wheels. Now my issue is this. It runs on after i shut it off. It dies after a few seconds. I cant keep the car running with the idle any lower. Manifold vacuum is a steady 10.5. secondly when i try to do a brake stand or apply the gas with my foot on the brake it pops and sputters out of the carb. a few times puffs of gray smoke have come out. The car is a 4sp and has 3.91's if it makes a difference. Anyone have any ideas on what to try next?